Biennial Report 2005-2007 - Saha Institute of Nuclear Physics

94 Biennial Report 2005-073.2.1.5 Implementation of Bio-inspired algorithms on TI DM642 processor for realtimeapplicationDeveloped bio-inspired algorithms related to Edge Detection, Enhancement and Interpolation havebeen implemented on a TI DM642 based hardware platform for real-time filtering and programmedfor post-processing of Ultrasound video frames from any standard Ultrasound machine, providingprocessed output suitable for normal display. This system has one video input channel, one videooutput channel, one video decoder, one video encoder and TI DM642@720 MHz DSP processor forreal-time processing. This system is capable of acquiring composite video in PAL/NTSC formatand can output video in VGA/SVGA/XGA @60fps. Though this system is used for post-processingof diagnostic ultrasound video it can be used for real-time processing of any PAL/NTSC video.Sandip Sarkar, Kuntal Ghosh, Subhajit KarmakarMED3.2.1.6 An alternative Gaussian window approach for FIR filter designWe have further extended our concept of modeling with combination Gaussians to FIR Digital FilterConstruction. With this technique we can construct FIR Digital Filters with a maximum stopbandattenuation of 300dB with negligible pass-band ripple on a 32-bit computational platform.Its computational requirement is much less than many popular techniques. The filter constructionprocedure is therefore very fast (probably the fastest). The lesser computational requirement makesit very suitable for also adaptive filtering applications. A GUI based Digital Filter Design Toolkithas been completed for making the techniques readily useful.Sandip Sarkar, Subhajit Karmakar, Kuntal Ghosh, Swapan SenMED3.2.1.7 Design of a low-pass filter by multi-scale even order Gaussian derivativesA new low-pass FIR filter design technique for achieving variable stopband attenuation withoutaltering the passband and stopband edges, is proposed. The filter function is a linear combinationof multi-scale Gaussian derivatives. In the frequency domain, the spectral modes correspondingto the continuous Gaussian derivatives have monotonic tails. In discrete domain, this amounts tovariable stopband attenuation which depends upon the truncation length of the continuous kernel,the scale and the order of Gaussian derivatives. The proposed algorithm consists of derivation ofsome useful mathematical relations between the basic design parameters and the parameters of theGaussian derivatives and an optimization technique that finally produces an equiripple passbandlowpass FIR filter with a higher falloff rate at the beginning of the transition band. Such a filterwith variable stopband attenuation may be effective at the time of reconstruction of the desiredpassband signal in a σδ modulator outpuSubhajit Karmakar, Kuntal Ghosh, Sandip Sarkar, Swapan SenMED